Displacement detection system of an optical touch panel and method thereof

ABSTRACT

At a first time, an image sensor captures a first image including images of an object. At a second time, the image sensor captures a second image including images of the object. A coordinate calculation device calculates a first coordinate of the object at the first time according to the first image, and a second coordinate of the object at the second time according to the second image. A coordinate correction device calculates a displacement between the first time and the second time according to the first coordinate and the second coordinate, and corrects an output coordinate of the object at the second time according to the displacement.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of applicant'searlier application Ser. No. 12/826,638, filed 2010 Jun. 29, and isincluded herein by reference. The Ser. No. 12/826,638 application claimsthe benefit of U.S. Provisional Application No. 61/221,565, filed onJun. 30, 2009 and entitled “COORDINATE DETECTION OF TOUCH SYSTEM,” thecontents of which are also incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a displacement detection system of anoptical touch panel and method thereof, and more particularly, to adisplacement detection system of an optical touch panel and methodthereof capable of correcting output coordinates according to adisplacement.

2. Description of the Prior Art

A traditional optical touch panel utilizes a light source to light apanel, and an image sensor to capture an image including an image of anobject. The optical touch panel utilizes luminance information of theobject to calculate a center of gravity of the object, so the center ofgravity of the object obtained according to the luminance information ofthe object may be biased to one side of the panel when the object movesacross corners of the panel. In this situation, although the objectmoves straight forward, the image sensor may capture a curved image ofthe object when the object moves across corners of the panel. Pleaserefer to FIG. 1. FIG. 1 is a diagram illustrating the image sensorcapturing the uncorrected image of the object when the object movesacross corners of the panel. As shown in FIG. 1, the center of gravityof the object obtained according to the luminance information of theobject may be biased to one side of the panel because the object movesfrom a light/dark area to a light/dark area of the panel.

The prior art utilizes a center of the object to calculate shadow pointsfor improving the above mentioned situation. But quality ofinterpolation calculation is poor in the prior art utilizing the centerof the object, and may result in sawtooth images appearing when theobject moves slowly.

SUMMARY OF THE INVENTION

An embodiment of the present invention provides a displacement detectionsystem of an optical touch panel. The displacement detection systemcomprises a panel, at least one first image sensor and a second imagesensor, a coordinate calculation device, and a coordinate correctiondevice. The panel is used for being touched by an object. The firstimage sensor and the second image sensor are installed on differentpositions of the panel, and view of the first image sensor and view ofthe second image sensor are overlapped. The coordinate calculationdevice is used for utilizing the first image sensor and the second imagesensor to capture a first image and a second image including images ofthe object respectively at a first time, utilizing image positions ofthe object in the first image and the second image to calculate a firstcoordinate of the object at the first time, utilizing the first imagesensor and the second image sensor to capture a third image and a fourthimage including images of the object respectively at a second time, andutilizing image positions of the object in the third image and thefourth image to calculate a second coordinate of the object at thesecond time. The coordinate correction device is used for calculating adisplacement of the object between the first time and the second timeaccording to the first coordinate and the second coordinate, and forcorrecting an output coordinate of the object at the second timeaccording to the displacement.

Another embodiment of the present invention provides a displacementdetection method of an optical touch panel. The displacement detectionmethod comprises capturing a first image including an object by a firstimage sensor and a second image including the object by a second imagesensor on a panel at a first time; capturing a third image including theobject by the first image sensor and a fourth image including the objectby the second image sensor on the panel at a second time; calculating afirst coordinate of the object at the first time according to imagepositions of the object in the first image and the second image;calculating a second coordinate of the object at the second timeaccording to image positions of the object in the third image and thefourth image; calculating a displacement of the object between the firsttime and the second time according to the first coordinate and thesecond coordinate; correcting an output coordinate of the object at thesecond time according to the displacement.

Another embodiment of the present invention provides a displacementdetection system of an optical touch panel. The displacement detectionsystem comprises a panel, at least one first image sensor and a secondimage sensor, a coordinate calculation device, and a coordinatecorrection device. The panel is used for being touched by an object. Thefirst image sensor and the second image sensor are installed ondifferent positions of the panel, and view of the first image sensor andview of the second image sensor are overlapped. The coordinatecalculation device is used for saving an initial coordinate of theobject on the panel at an initial time, utilizing the first image sensorand the second image sensor to capture a first image and a second imageincluding images of the object respectively at a first time, andutilizing image positions of the object in the first image and thesecond image to calculate a first coordinate of the object at the firsttime. And the coordinate correction device is used for calculating adisplacement of the object between the initial time and the first timeaccording to the initial coordinate and the first coordinate, and forcorrecting an output coordinate of the object at the first timeaccording to the displacement.

The present invention provides a displacement detection system of anoptical touch panel and method thereof. The displacement detectionsystem of an optical touch panel and method thereof generate an adaptingsmoothing parameter according to a displacement of an object between twodifferent time points. Then, based on a relationship between a velocityof the object and an image position at the last time is reverse, thepresent invention utilizes the adapting smoothing parameter to givedifferent weighted values to the image positions of the two differenttime points. Therefore, a moving trace of the object corrected by theweighted values may not be influenced when the object moves from thelight/dark area to the light/dark area of the panel.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the image sensor capturing theuncorrected image of the object when the object moves across corners ofthe panel.

FIG. 2 is a diagram illustrating a displacement detection system of anoptical touch panel according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a displacement detection system of anoptical touch panel according to another embodiment of the presentinvention.

FIG. 4 is a flowchart illustrating a displacement detection method of anoptical touch panel according to another embodiment of the presentinvention.

DETAILED DESCRIPTION

Please refer to FIG. 2. FIG. 2 is a diagram illustrating a displacementdetection system 200 of an optical touch panel according to anembodiment of the present invention. The displacement detection system200 comprises a panel 202, a first light source 204, a second lightsource 206, a first image sensor 208, a second image sensor 210, acoordinate calculation device 212, a smoothing parameter generatingdevice 214, and a coordinate correction device 216. The panel 202 isused for being touched by an object. The first light source 204 and thesecond light source 206 are used for lighting the panel 202. The firstimage sensor 208 and the second image sensor 210 are installed ondifferent positions of the panel 202, and view of the first image sensor208 and view of the second image sensor 210 are overlapped. At a firsttime, the first image sensor 208 and the second image sensor 210 capturea first image and a second image including images of the objectrespectively, and at a second time, the first image sensor 208 and thesecond image sensor 210 capture a third image and a fourth imageincluding images of the object respectively. The coordinate calculationdevice 212 is coupled to the first image sensor 208 and the second imagesensor 210 for using image positions of the object in the first imageand the second image to calculate a first coordinate D1 of the object atthe first time, and using image positions of the object in the thirdimage and the fourth image to calculate a second coordinate D2 of theobject at the second time. The coordinate correction device 216 iscoupled to the coordinate calculation device 212 for calculating adisplacement Z of the object between the first time and the second timeaccording to the first coordinate D1 and the second coordinate D2.

The smoothing parameter generating device 214 is coupled to thecoordinate correction device 216 for substituting the displacement Zinto equation (1) to generate an adaptive smoothing parameter λ:

$\begin{matrix}{{\lambda = {k\frac{1}{\sqrt{\left( {{y_{i}\;(t)} - {y_{o}\left( {t - 1} \right)}} \right)^{2} + \left( {{x_{i}(t)} - {x_{o}\left( {t - 1} \right)}} \right)^{2}}}}},{0 \leq \lambda \leq 1}} & (1)\end{matrix}$

where k is an adaptive smoothing constant, y_(i)(t) is an uncorrected ycoordinate of the object at the second time, y_(o)(t−1) is a corrected ycoordinate of the object at the first time, x_(i)(t) is an uncorrected xcoordinate of the object at the second time, and x_(o)(t−1) is acorrected x coordinate of the object at the first time.

According to the adaptive smoothing parameter λ, the coordinatecorrection device 216 corrects the image positions of the object in thefirst image and the second image to obtain a first weighted imageposition (λx_(o)(t−1),λy_(o)(t−1)), and corrects the image positions ofthe third image and the fourth image to obtain a second weighted imageposition ((1−λ)x_(i)(t),(1−λ)y_(i)(t)). Then, the coordinate correctiondevice 216 calculates the output coordinate (x_(o)(t), y_(o)(t)) at thesecond time according to the first weighted image (λx_(o)(t−1),λy_(o)(t−1)) position, the second weighted image position((1−λ)x_(i)(t),(1−λ)y_(i)(t)), and equations (2):y _(o)(t)=(1−λ)y _(i)(t)+λy _(o)(t−1)x _(o)(t)=(1−λ)x _(i)(t)+λx _(o)(t−1)  (2)where y_(o)(t) is a corrected y coordinate of the object at the secondtime, and x_(o)(t) is a corrected x coordinate of the object at thesecond time. A concept of using the adaptive smoothing parameter λ tocorrect image positions of the object to obtain the weighted imageposition is based on correlation between position of the object andimage position at the last time being low/high if the object movesfast/slow. Therefore, a relationship between the adaptive smoothingparameter λ and a velocity of the object is reverse according to theequation (1) and the abovementioned concept. A weighted value for theimage position of the first time is λ and a weighted value for the imageposition of the second time is 1−λ.

Please refer to FIG. 3. FIG. 3 is a diagram illustrating a displacementdetection system 300 of an optical touch panel according to anotherembodiment of the present invention. The displacement detection system300 uses the coordinate calculation device 212 to save initialcoordinate C0 of the object on the panel 202 at an initial time. Thecoordinate calculation device 212 uses the first image sensor 208 andthe second image sensor 210 to capture a first image and a second imageincluding images of the object respectively at a first time, and usesimage positions of the object in the first image and the second image tocalculate first coordinate C1 of the object at the first time. Thecoordinate correction device 212 calculates a displacement Z1 of theobject between the initial time and the first time according to theinitial coordinate C0 and the first coordinate C1. After obtaining thedisplacement Z1, subsequent operation steps of the displacementdetection system 300 are the same as for the displacement detectionsystem 200, so further description thereof is omitted for simplicity. Itshould be noted that, the initial coordinate C0 is an uncorrectedcoordinate but D1 in FIG. 2 is a corrected coordinate.

Please refer to FIG. 4. FIG. 4 is a flowchart illustrating adisplacement detection method of an optical touch panel according toanother embodiment of the present invention. FIG. 4 uses thedisplacement detection system 200 in FIG. 2 to illustrate the method.Detailed steps are as follows:

Step 400: Start.

Step 402: At the first time, the first image sensor 208 captures thefirst image including the object on the panel 202, and the second imagesensor 210 captures the second image including the object on the panel202.

Step 404: At the second time, the first image sensor 208 captures thethird image including the object on the panel 202, and the second imagesensor 210 captures the fourth image including the object on the panel202.

Step 406: The coordinate calculation device 212 calculates the firstcoordinate D1 of the object at the first time according to imagepositions of the object in the first image and the second image.

Step 408: The coordinate calculation device 212 calculates the secondcoordinate D2 at the second time according to image positions of theobject in the third image and the fourth image.

Step 410: The coordinate correction device 216 calculates thedisplacement Z of the object between the first time and the second timeaccording to the first coordinate D1 and the second coordinate D2.

Step 412: The smoothing parameter generating device 214 generates theadaptive smoothing parameter λ according to the displacement Z.

Step 414: The coordinate correction device 216 corrects an outputcoordinate of the object at the second time according to adaptivesmoothing parameter λ.

Step 416: End.

To sum up, the displacement detection system of an optical touch paneland method thereof provided by the present invention generate theadaptive smoothing parameter according to the displacement between twodifferent time points. Then, based on the correlation between theposition of the object and the image position at the last time beinglow/high if the object moves fast/slow, the present invention utilizesthe adaptive smoothing parameter to give different weighted values tothe image positions of the two different time points. Therefore, amoving trace of the object corrected by the weighted values may not beinfluenced when the object moves from the light/dark area to thelight/dark area of the panel.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A displacement detection system of an optical touch panel,comprising: a panel for being touched by an object; an image sensor; acoordinate calculation device for utilizing the image sensor to capturea first image including images of the object at a first time, utilizingimage positions of the object in the first image to calculate a firstcoordinate of the object at the first time, utilizing the image sensorto capture a second image including images of the object at a secondtime, and using image positions of the object in the second image tocalculate a second coordinate of the object at the second time; and acoordinate correction device for calculating a displacement of theobject between the first time and the second time according to the firstcoordinate and the second coordinate, and for correcting an outputcoordinate of the object at the second time according to thedisplacement.
 2. The displacement detection system of claim 1, furthercomprising a light source for lighting the panel.
 3. The displacementdetection system of claim 1, wherein the coordinate correction devicecorrects the image positions of the object in the first image accordingto the displacement to obtain a first weighted image position, correctsthe image positions of the object in the second image according to thedisplacement to obtain a second weighted image position, and calculatesthe output coordinate according to the first weighted image position andthe second weighted image position.
 4. The displacement detection systemof claim 1, further comprising a smoothing parameter generating devicefor generating an adaptive smoothing parameter according to thedisplacement and the following equation:${\lambda = {k\frac{1}{\sqrt{\left( {{y_{i}\;(t)} - {y_{o}\left( {t - 1} \right)}} \right)^{2} + \left( {{x_{i}(t)} - {x_{o}\left( {t - 1} \right)}} \right)^{2}}}}},{{0 \leq \lambda \leq 1};}$wherein λ is the adaptive smoothing parameter; k is an adaptivesmoothing constant; y_(i)(t) is an uncorrected y coordinate of theobject at the second time; y_(o)(t−1) is a corrected y coordinate of theobject at the first time; x_(i)(t) is an uncorrected x coordinate of theobject at the second time; and x_(o)(t−1) is a corrected x coordinate ofthe object at the first time; wherein the coordinate correction devicecorrects the output coordinate at the second time according to theadaptive smoothing parameter.
 5. The displacement detection system ofclaim 4, wherein the operation that the coordinate correction devicecorrects the output coordinate at the second time according to theadaptive smoothing parameter is according to the following equations:y _(o)(t)=(1−λ)y _(i)(t)+λy _(o)(t−1);x _(o)(t)=(1−λ)x _(i)(t)+λx _(o)(t−1); wherein y_(o)(t) is a corrected ycoordinate of the object at the second time; and x_(o)(t) is a correctedx coordinate of the object at the second time.
 6. A displacementdetection method of an optical touch panel, comprising: capturing afirst image including an object by a image sensor on a panel at a firsttime; capturing a second image including the object by the image sensoron the panel at a second time; calculating a first coordinate of theobject at the first time according to image positions of the object inthe first image; calculating a second coordinate of the object at thesecond time according to image positions of the object in the secondimage; calculating a displacement of the object between the first timeand the second time according to the first coordinate and the secondcoordinate; and correcting an output coordinate of the object at thesecond time according to the displacement.
 7. The displacement detectionmethod of claim 6, wherein correcting the output coordinate of theobject at the second time according to the displacement comprises:correcting the image positions of the object in the first imageaccording to the displacement to obtain a first weighted image position;correcting the image positions of the object in the second imageaccording to the displacement to obtain a second weighted imageposition; and correcting the output coordinate according to the firstweighted image position and the second weighted image position.
 8. Thedisplacement detection method of claim 6, further comprising generatingan adaptive smoothing parameter according to the displacement and thefollowing equation, and correcting the output coordinate at the secondtime according to the adaptive smoothing parameter:${\lambda = {k\frac{1}{\sqrt{\left( {{y_{i}\;(t)} - {y_{o}\left( {t - 1} \right)}} \right)^{2} + \left( {{x_{i}(t)} - {x_{o}\left( {t - 1} \right)}} \right)^{2}}}}},{{0 \leq \lambda \leq 1};}$wherein λ is the adaptive smoothing parameter; k is an adaptivesmoothing constant; y_(i)(t) is an uncorrected y coordinate of theobject at the second time; y_(o)(t−1) is a corrected y coordinate of theobject at the first time; x_(i)(t) is an uncorrected x coordinate of theobject at the second time; and x_(o)(t−1) is a corrected x coordinate ofthe object at the first time.
 9. The displacement detection method ofclaim 8, wherein correcting the output coordinate at the second timeaccording to the adaptive smoothing parameter is performed according tothe following equations:y _(o)(t)=(1−λ)y _(i)(t)+λy _(o)(t−1);x _(o)(t)=(1−λ)x _(i)(t)+λx _(o)(t−1); wherein y_(o)(t) is a corrected ycoordinate of the object at the second time; and x_(o)(t) is a correctedx coordinate of the object at the second time.
 10. A displacementdetection system of an optical touch panel, comprising: a panel forbeing touched by an object; an image sensor; a coordinate calculationdevice for saving an initial coordinate of the object on the panel at aninitial time, utilizing the image sensor to capture a first imageincluding images of the object at a first time, and utilizing imagepositions of the object in the first image to calculate a firstcoordinate of the object at the first time and a coordinate correctiondevice for calculating a displacement of the object between the initialtime and the first time according to the initial coordinate and thefirst coordinate, and for correcting an output coordinate of the objectat the first time according to the displacement.
 11. The displacementdetection system of claim 10, further comprising a smoothing parametergenerating device for generating an adapting smoothing parameteraccording to the displacement and the following equation, and forcorrecting the output coordinate at the first time according to theadaptive smoothing parameter:${\lambda = {k\frac{1}{\sqrt{\left( {{y_{i}\;(t)} - {y_{o}\left( {t - 1} \right)}} \right)^{2} + \left( {{x_{i}(t)} - {x_{o}\left( {t - 1} \right)}} \right)^{2}}}}},{{0 \leq \lambda \leq 1};}$wherein λ is the adaptive smoothing parameter; k is an adaptivesmoothing constant; y_(i)(t) is an uncorrected y coordinate of theobject at the first time; y_(o)(t−1) is a y coordinate of the object atthe initial time; x_(i)(t) is an uncorrected x coordinate of the objectat the first time; and x_(o)(t−1) is a x coordinate of the object at theinitial time.
 12. The displacement detection system of claim 11, whereinthe operation that the coordinate correction device corrects an outputcoordinate of the object at the first time according to the displacementis performed according to the following equations:y _(o)(t)=(1−λ)y _(i)(t)+λy _(o)(t−1);x _(o)(t)=(1−λ)x _(i)(t)+λx _(o)(t−1); wherein y_(o)(t) is a corrected ycoordinate of the object at the first time; and x_(o)(t) is a correctedx coordinate of the object at the first time.